R1-2508684
discussion
Discussion on 6GR Waveform
From Xiaomi
Summary
Xiaomi provides 3 proposals and 2 observations on 6GR waveform, focusing on DL DFT-s-OFDM for NTN coverage enhancement and UL 6GR waveform starting points. They propose applying low-PAPR DFT-s-OFDM to specific DL channels (PDCCH CSS, Msg4 PDSCH, SIB1 PDSCH) and analyzing multi-user/channel multiplexing tradeoffs involving FDM with PAPR increase or multiple RF chains.
Position
Xiaomi proposes adopting DL DFT-s-OFDM as a low-PAPR waveform for NTN coverage enhancement, specifically targeting PDCCH CSS (except type-3), Msg4 PDSCH, and SIB1 PDSCH, citing Rel-19 repetition mechanism drawbacks including fragmented configuration and insufficient repetition times. They present two FDM multi-user multiplexing approaches (MU-MUX1 with multiple DFT operations and MU-MUX2 with single DFT operation and per-UE DMRS) and observe that FDM for multi-user or multi-channel multiplexing incurs PAPR increase or requires additional RF chains respectively. For UL 6GR waveform, they propose reusing Rel-18 coverage enhancement mechanisms including MPR reduction allowing 1dB power boosting and dynamic waveform switching via transform precoder indicator in DCI formats 0_1/0_2.
Key proposals
- Proposal 1 (Sec 2.1): To support the coverage performance for NTN DL, low-PAPR waveform such as DFT-S-OFDM can be considered.
- Proposal 2 (Sec 2.1.1): To support the coverage performance for NTN DL, low-PAPR waveform can be applied to the following channels: PDCCH at least for CSS (except for type-3), PDSCH with Msg 4, PDSCH with SIB1.
- Proposal 3 (Sec 2.2): The UL coverage enhancement mechanism in Rel-18 including power domain solution and waveform switch related solution can be taken as a starting point for UL coverage performance guarantee for both TN and NTN.
- Observation 1 (Sec 2.1.2): For DL DFT-s-OFDM waveform, apart from TDM, FDM can be used for multi-user multiplexing at the cost of certain PAPR increase.
- Observation 2 (Sec 2.1.3): For DL DFT-s-OFDM waveform, apart from TDM, FDM can be used for multi-channel multiplexing at the cost of increased number of RF chains.